function [z] = FISTA(y, A, lambda, delta)

x_pre = A'*y;
t = 1;
z = x_pre;
z_pre = z;
t_pre = t;
N = size(A, 2);
diff = 1;
E = eig(A'*A);
L = E(end);
temp1 = A'*y/L;
temp2 = eye(N) - A'*A/L;
k = 0;
while((diff > delta) && (k < 1000))
    temp = temp1 + temp2 * z_pre;
    x = sft_thd(temp, lambda/L);
    t = 0.5*(1 + sqrt(1+4*t_pre*t_pre));
    z = x + (x - x_pre) * (t_pre-1) / t;
    diff = mean(abs(z_pre - z)); 
    x_pre = x;
    z_pre = z;
    t_pre = t;
    k = k + 1;
end

end